Lighting systems are formed typically by interconnecting many light fixtures by a communications system and providing for operator control from a central controller. Such lighting systems may contain multiparameter light fixtures, which illustratively are light fixtures having two or more individually remotely adjustable parameters such as beam size, color, shape, angle, and other light characteristics. Multiparameter light fixtures are widely used in the lighting industry because they facilitate significant reductions in overall lighting system size and permit dynamic changes to the final lighting effect. Applications and events in which multiparameter light fixtures are used to great advantage include showrooms, television lighting, stage lighting, architectural lighting, live concerts, and theme parks. Illustrative multi-parameter light devices are described in the product brochure entitled “The High End Systems Product Line 2001” and are available from High End Systems, Inc. of Austin, Tex.
Prior to the advent of relatively small commercial digital computers, remote control of light fixtures from a central controller was done with either a high voltage or low voltage current; see, e.g., U.S. Pat. No. 3,706,914, issued Dec. 19, 1972 to Van Buren, and U.S. Pat. No. 3,898,643, issued Aug. 5, 1975 to Ettlinger, which are incorporated by reference herein. With the widespread use of computers, digital serial communications over wire was widely adopted as a way to achieve remote control; see, e.g., U.S. Pat. No. 4,095,139, issued Jun. 13, 1978 to Symonds et al., and U.S. Pat. No. 4,697,227, issued Sep. 29, 1987 to Callahan, incorporated by reference herein. In 1986, the United States Institute of Theatre Technology (“USITT”) developed a digital communications system protocol for multi-parameter light fixtures known as DMX512. Basically, the DMX512 protocol is comprised of a stream of data which is communicated one-way from the control device to the light fixture using an Electronics Industry Association (“EIA”) standard for multipoint communications know as RS-485.
A variety of different types of multiparameter light fixtures are available. One type of advanced multiparameter light fixture which is referred to herein as an image projection lighting device (“IPLD”) uses a light valve to project images onto a stage or other projection surface. A light valve, which is also known as an image gate, is a device for example such as a digital micro-mirror (“DMD”) or a liquid crystal display (“LCD”) that forms the image that is projected. U.S. Pat. No. 6,057,958, issued May 2, 2000 to Hunt, incorporated herein by reference, discloses a pixel based gobo record control format for storing gobo images in the memory of a light fixture. The gobo images can be recalled and modified from commands sent by a control console. A pixel based gobo image is a gobo (or a projection pattern) created by a light valve like a video projection of sorts. U.S. Pat. No. 5,829,868, issued Nov. 3, 1998 to Hutton, incorporated by reference herein, discloses storing video frames as cues locally in a lamp, and supplying them as directed to the image gate to produce animated and real-time imaging. A single frame can also be manipulated through processing to produce multiple variations. Alternatively, a video communication link can be employed to supply continuous video from a remote source.
U.S. Pat. No. 5,828,485, issued Oct. 27, 1998 to Hewlett, incorporated herein by reference, discloses the use of a camera with a digital micro mirror equipped light fixture for the purpose of following the shape of the performer and illuminating the performer using a shape that adaptively follows the performer's image. A camera capturing the image (such as a digital camera, which captures an image at least in part by storing digital data in computer memory, the digital data which defining or describing the image) preferably is located at the lamp illuminating the scene in order to avoid parallax. The image can be manually investigated at each lamp or downloaded to some central processor for this purpose.
U.S. patent application Ser. No. 10/090,926, titled “METHOD, APPARATUS AND SYSTEM FOR IMAGE PROJECTION LIGHTING”, inventor Richard S. Belliveau, publication no. 20020093296, filed on Mar. 4, 2002, incorporated by reference herein, describes prior art IPLDs with cameras and communication systems that allow camera content, such as in the form of digital data, to be transferred between prior art IPLDs.
IPLDs of the prior art use light from the main projection lamp that is sent though a light valve and focused by an output lens to project images on a stage. The light cast upon the stage by the IPLD is then imaged by the camera. U.S. Pat. No. 6,219,093 to Perry titled “Method and device for creating the facsimile of an image”, incorporated herein by reference describes a camera that may be an infrared camera for use with a described lighting device that uses liquid crystal light valves to project an image. “Accordingly the camera and light are mounted together for articulation about x, y, and z axes as is illustrated in FIG. 1” (Perry, U.S. Pat. No. 6,219,093, col. 4, line 59).
The prior art patent to Perry, U.S. Pat. No. 6,219,093 makes use of a camera to distinguish objects in the camera's field from other objects. The distinguished object as imaged by the camera is then illuminated by the projected light passing through the light valves so as to only illuminate the distinguished object. The objects may be provided with an infrared emitter or reflector which interacts with a receiver or camera. Perry relies on the light produced from the projection lamp and the light valves to provide the illumination to the scene where the camera images or separate emitters or reflectors are provided with the objects on the stage. The Perry prior art patent describes its invention as a camera/light unit.
For IPLDs having a main projection lamp, a camera, and a light valve it would be desirable to superimpose an optical path of the camera with an optical path of the main projection lamp so that the two paths are coaxial. In this manner the images that are created by the main projection lamp and the light valve, that are projected onto the projection surface, and that are captured by the camera on the projection surface will be directly centered. There are several problems associated with superimposing the camera and the main projection lamp optical paths. One method involves using beam splitters as known in the optics art for superimposing two optical paths however beam splitters are known to produce a compromise where neither optical path will operate at its best efficiency. For example a 50% beam splitter could be used to provide 50% transmission of the light from the main projection lamp optical system towards the projection surface while allowing returning light from the projection surface to be reduced by 50% as it is captured by the camera. Various percentages can be managed such as 70% transmission of light from the main projection lamp optical system and 30% returning light to be captured by the camera as known in the optics art. The use of beam splitters for superimposing the camera optical path and the main projection lamp optical path requires unacceptable compromises.
Another method as known in the optics art is the pick off some of the light reflected from a projection surface towards the center of a main focusing lens. A small mirror can be located at the center of the main projection lens where light reflected from the projection surface can be directed at an angle towards the camera optical path by the small mirror while light projecting from the lens towards the projection surface is minimized only by the blockage of the small mirror. Depending on the size of the mirror used to pick off some of the light, the main projection lens is partially blocked resulting again in loss of efficiency of the main projection lamp optical system.